This is by no means taking a shot at Sencha's dev team, but it seems that the Radial axis needs serious rework. So, to whom this may concern:
 the "drawAxis" function assumes that the store count != 0 the first time when it is called. This is only true if the store has client-side data. Try loading a Radar chart using a "remote" store and the labels and axis drawn by the "drawAxis" function are not handled correctly.
The reason for this is because "drawAxis" wants to be smart by "caching" labels and axis sprites. So the first time when this function is called, the "remote" store has not loaded yet, therefore only the "circles" are cached, the "this.sprites" is set, but since there are no records in the store yet, no sprites are enabled for the labels and axis.
I think the best way to fix this is to split the "this.sprites" into 3 chunks (circles,axis and labels) and only draw/redraw sprites when necessary. At the moment all these sprites are added to "this.sprites"
 Please also fix the docs for the Radial. The class is marked as "private" which makes jsduck skipping it.
 (And this is the last one for this thread, I promise), Please use the "me." notation instead of "this.". Let us poor developers who read the codebase stay away from heart attack pills and keep our few remaining strain of hair.
Is the a chance you can create a bug report of any of this as it can be passed along as a bug report and feature request? I can currently pass this along as a feature request if that will suffice.
Please add my thread as a bug. There is really not much I can add at this moment. The Ext.chart.axis.Radial is simply broken. My text should provide sufficient information for the team to fix.